Known seal members are, for example, packers which are arranged in the borehole to seal an annular space between a wellbore casing and a production tubing extending into the borehole. Such packer is radially deformable between a retracted position in which the packer is lowered into the borehole, and an expanded position in which the packer forms a seal. Activation of the packer can be by mechanical or hydraulic means. A limitation of the applicability of such packers is that the seal surfaces have to be well defined.
Another type of annular seal member is formed by a layer of cement arranged in an annular space between a wellbore casing and the borehole wall. Although in general cement provides adequate sealing capability, there are some inherent drawbacks such as shrinking of the cement during hardening resulting in de-bonding of the cement sheath, or cracking of the cement layer after hardening, for example due to pressure and temperature shocks during operation of the well.
In view thereof there is a need for an improved wellbore system which provides adequate sealing of the annular space formed between a tubular element extending into the borehole and a cylindrical wall surrounding the tubular element.